The modern doctrine of tumors rests wholly on the basis of histogenesis. Some of the shortcomings and the objections to the present embryologic classification of tumors are noted by Klaatsch1 and by Charles Powell White.2 The former points out some of the inconsistencies which are creeping into our classification, and that the distinction between mesodermal and other structures of the body is in reality not as hard and fast as it is usually drawn. White emphasizes the fact that the developmental origin of some parts of the body is not yet fully explained; the present onkologic classification separates tumors that are not distinguishable histologically, such as some forms of carcinoma and endothelioma; some authors, for instance Ziegler, class tumors of epiblastic origin—the gliomas or neuro-epitheliomas—among the mesoblastic ones. In order to overcome these inconsistencies, and also in order to avoid all theories as to the as yet